Unconventional phase JANUS nanostructure for electrocatalytic carbon dioxide reduction

Abstract

The invention discloses a nano material. The nano material comprises an Au nano structure, and a Cu nanostructure provided with the Au nanostructure; wherein each of the Au nanostructures and the Cu nanostructures is in the form of a heterogeneous phase. The invention also discloses a method for preparing the nano material.

Description

Technical Field

[0001] The present invention relates to a nanomaterial, for example, particularly but not exclusively, a nanomaterial comprising Au nanostructures and Cu nanostructures, wherein each nanostructure is in a heterogeneous phase. The present invention also relates to a method for preparing the nanomaterial and to the use of the nanomaterial, in particular in an electrochemical carbon dioxide reduction reaction. Background Art

[0002] Since the Industrial Revolution, the concentration of carbon dioxide (CO2) in the Earth's atmosphere has increased dramatically by about 50% (from about 280 to 420 ppm), and this problem needs to be addressed urgently due to its severe negative impact on the global ecosystem and environment. Among different approaches, the electrochemical CO2 reduction reaction (CO2RR) that can use renewable electricity as a power source can convert excess accumulated CO2 into value-added chemicals and fuels, and therefore has high hopes for achieving carbon neutrality. Specifically, the multi-carbon (C 2+ ) products are more desirable because they have much higher energy content and greater economic value than single-carbon (C1) products.

[0003] Copper (Cu) is considered to be used for C 2+ The most unique catalyst produced is Cu-based nanomaterials because of its suitable adsorption strength for key intermediates in CO2RR. To date, a series of material design strategies have been applied to Cu-based nanomaterials to improve their adsorption of C 2+ The resulting catalytic properties include fine control over crystal facets, strain, defects, composition, size, and dimensionality. However, all of these previous material modification efforts are based on the conventional phase of Cu, namely face-centered cubic (fcc).

[0004] There have been reports on unconventional phase metallic nanomaterials, such as unconventional phase single metals (e.g., 4H gold (Au), 2H cobalt, fcc ruthenium) and bimetallic alloys (e.g., 2H platinum nickel, 2H nickel iron, body-centered cubic palladium copper), but the synthesis of unconventional phase Cu-based heterogeneous nanomaterials, especially those with site-selective growth of Cu on template / base / substrate materials such as unconventional phase Au-based nanomaterials, remains a challenge.

[0005] The present invention seeks to eliminate or at least alleviate such problems by providing new or otherwise improved methods for site-selectively growing Au-Cu nanomaterials. Summary of the Invention

[0006] In a first aspect of the present invention, there is provided a nanomaterial comprising: an Au nanostructure; and a Cu nanostructure provided with the Au nanostructure; wherein each of the Au nanostructure and the Cu nanostructure is in a different phase.

[0007] Optionally, Cu nanostructures are provided on and over the Au nanostructures.

[0008] Optionally, both the Au nanostructures and the Cu nanostructures are in the form of fcc-2H-fcc heterophase structures.

[0009] Optionally, the Cu nanostructure covers the first portion of the Au nanostructure.

[0010] Optionally, the second portion of the Au nanostructure is covered with a surfactant.

[0011] In an optional embodiment, the Au nanostructures are in the form of fcc-2H-fcc Au nanorods.

[0012] Optionally, the fcc-2H-fcc Au nanorods have a first portion covered by the fcc-2H-fcc Cu nanostructures.

[0013] Optionally, the fcc-2H-fcc Au nanorods and fcc-2H-fcc Cu nanostructures are arranged in a substantially lattice-matched manner.

[0014] Optionally, the fcc-2H-fcc Au nanorods include a second portion at least partially covered by a surfactant.

[0015] Optionally, the surfactant comprises any one of oleylamine and dodecylamine.

[0016] In an optional embodiment, the fcc-2H-fcc Au nanostructures and the fcc-2H-fcc Cu nanostructures are arranged in the form of a Janus nanostructure.

[0017] Optionally, a first portion of the fcc-2H-fcc Au nanorods is circumferentially covered by the fcc-2H-fcc Cu nanostructures.

[0018] Optionally, the first portion is arranged between two second portions on the fcc-2H-fcc Au nanorods, and at least one of the two second portions is at least partially covered by a surfactant.

[0019] Optionally, at least one of the two second portions is at least partially covered by fccCu atoms of the fcc-2H-fcc Cu nanostructure.

[0020] In an optional embodiment, the fcc-2H-fcc Au nanorods and the fcc-2H-fcc Cu nanostructures are arranged in the form of a coaxial heterostructure.

[0021] Optionally, the fcc-2H-fcc Au nanorods are wrapped by fcc-2H-fcc Cu nanostructures.

[0022] In an optional embodiment, the fcc-2H-fcc Au nanorods and the fcc-2H-fcc Cu nanostructures are arranged in the form of fcc-2H-fcc Au-Cu core-shell nanostructures.

[0023] In a second aspect of the present invention, there is provided a method for preparing the nanomaterial according to the first aspect, the method comprising the following steps:

[0024] a) providing a reaction mixture comprising fcc-2H-fcc Au nanostructures, a reducing agent, and a copper precursor; b) heating the reaction mixture for a predetermined time, and then cooling the reaction mixture to room temperature; and c) separating the nanomaterial from the reaction mixture.

[0025] Optionally, the reaction mixture further comprises a surfactant.

[0026] Optionally, the reaction mixture is provided by adding a copper precursor at a predetermined rate to a solution mixture comprising fcc-2H-fcc Au nanostructures, a surfactant, and a reducing agent at an elevated temperature.

[0027] Optionally, the reducing agent comprises any one of 1,2-hexanediol, 1,2-hexadecanediol, and 1,2-butanediol.

[0028] Optionally, the surfactant comprises a mixture of oleylamine and dodecylamine.

[0029] Optionally, oleylamine and dodecylamine have a volume ratio of about 2:3.

[0030] Optionally, the copper precursor comprises copper acetylacetonate.

[0031] In an optional embodiment, when the reducing agent comprises 1,2-hexanediol, the copper precursor is reacted at a rate of about 0.094 mL min -1 was added to the solution mixture at a rate of .

[0032] In an optional embodiment, when the reducing agent comprises 1,2-hexadecanediol, the copper precursor is reacted at a rate of about 0.062 mL min -1 was added to the solution mixture at a rate of .

[0033] In an optional embodiment, when the reducing agent comprises 1,2-butanediol, the copper precursor is reacted at about 0.5 mL s -1 was added to the solution mixture at a rate of .

[0034] Optionally, the elevated temperature is from about 110°C to about 130°C.

[0035] Optionally, the fcc-2H-fcc Au nanostructures are provided in the form of fcc-2H-fcc Au nanorods.

[0036] In an optional embodiment, the method is a seed growth method.

[0037] In a third aspect of the present invention, a catalyst for electrochemical carbon dioxide reduction reaction is provided, wherein the catalyst comprises the nanomaterial according to the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0039] Figure 1 Schematic diagram showing the site-selective growth of Cu to form unconventional phase Au-Cu heteronanostructures on fcc-2H-fcc Au NRs according to an embodiment of the present invention. HDO, 1,2-hexanediol; HDD, 1,2-hexadecanediol; BDO, 1,2-butanediol; Cu(acac)2, copper acetylacetonate;

[0040] Figure 2A TEM image of as-synthesized fcc-2H-fcc Au NR is shown, with a scale of 50 nm.

[0041] Figure 2B TEM image of the as-synthesized fcc-2H-fcc Au NR is shown, with a scale of 20 nm;

[0042] Figure 3A Statistical analysis of the length of the as-synthesized fcc-2H-fcc Au NRs is shown;

[0043] Figure 3B Statistical analysis of the width of the as-synthesized fcc-2H-fcc Au NRs is shown;

[0044] Figure 4A Typical HRTEM images of fcc-2H-fcc Au NRs are shown;

[0045] Figure 4B Shown along

[110] h /

[101] f Crystal model of a typical fcc-2H-fcc Au NR observed by zone axis;

[0046] Figure 5The XRD pattern of the as-synthesized fcc-2H-fcc Au NR is shown; the characteristic peaks of the 2H and fcc phases are marked in the XRD pattern, confirming the fcc-2H-fcc heterogeneous phase of the obtained Au NR;

[0047] Figure 6 The XPS spectrum of fcc-2H-fcc Au NR is shown, indicating the metallic state of Au in fcc-2H-fcc NR.

[0048] Figure 7 shows the EDS analysis of the composition of fcc-2H-fcc Au-Cu heteronanostructures, where fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CAH, and fcc-2H-fcc Au-Cu CSN have Au / Cu atomic ratios of 47.38 / 52.62, 37.23 / 62.77, and 18.02 / 81.98, respectively;

[0049] Figure 8A TEM images of fcc-2H-fcc Au-Cu JNS are shown;

[0050] Figure 8B HAADF-STEM image of fcc-2H-fcc Au-Cu JNS is shown;

[0051] Figure 8C The definition of the Cu domain thickness of fcc-2H-fcc Au-Cu JNS is shown;

[0052] Figure 8D Statistical analysis of the Cu domain thickness of fcc-2H-fcc Au-Cu JNS is shown;

[0053] Figure 9 shows the spherical aberration-corrected high-resolution HAADF-STEM image of the Au / Cu interface in fcc-2H-fcc Au-Cu JNS;

[0054] Figure 10A The unit cell of the conventional fcc phase (top image) and (101) are shown. f Schematic diagram of the plane (bottom figure);

[0055] Figure 10B The unit cell of the unconventional 2H phase (top image) and (110) are shown. h Schematic diagram of the plane (bottom panel);

[0056] Figure 11 is the HAADF-STEM image of a typical fcc-2H-fcc Au-Cu JNS and the corresponding EDS elemental mapping;

[0057] Figure 12 Shown along

[110] h /

[101] f Crystal model of the obtained fcc-2H-fcc Au-Cu JNS observed by zone axis;

[0058] Figure 13A TEM images of fcc-2H-fcc Au NRs dispersed in EG are shown, with a scale of 20 nm.

[0059] Figure 13B TEM images of fcc-2H-fcc Au-Cu JNS obtained by using EG as solvent are shown, with a scale of 50 nm.

[0060] Figure 14A The synthesis of fcc-2H-fcc Au-Cu JNS was shown using 1.86 mL min -1 TEM images of the products obtained with Cu precursor injection speed of , with a scale of 20 nm;

[0061] Figure 14B The synthesis of fcc-2H-fcc Au-Cu JNS was shown using 1.40 mL min -1 TEM images of the products obtained with Cu precursor injection speed of , with a scale of 20 nm;

[0062] Figure 14C The synthesis of fcc-2H-fcc Au-Cu JNS was shown using 0.064 mL min -1 TEM images of the products obtained with Cu precursor injection speed of , with a scale of 20 nm;

[0063] Figure 14D The synthesis of fcc-2H-fcc Au-Cu JNS was shown using 0.031 mL min -1 TEM images of the products obtained with Cu precursor injection speed of , with a scale of 20 nm;

[0064] Figure 15A TEM image of the product obtained after synthesis of fcc-2H-fcc Au-Cu JNS using a Cu precursor concentration of 5.20 mM is shown, with a scale of 20 nm;

[0065] Figure 15B TEM image of the product obtained after synthesis of fcc-2H-fcc Au-Cu JNS using a Cu precursor concentration of 9.20 mM is shown, with a scale of 20 nm;

[0066] Figure 15CTEM image of the product obtained after synthesis of fcc-2H-fcc Au-Cu JNS using a Cu precursor concentration of 17.20 mM is shown, with a scale of 20 nm;

[0067] Figure 15D TEM image of the product obtained after synthesis of fcc-2H-fcc Au-Cu JNS using a Cu precursor concentration of 20.40 mM is shown, with a scale of 20 nm;

[0068] Figure 16A TEM images of fcc-2H-fcc Au-Cu CAH are shown, with a scale of 50 nm;

[0069] Figure 16B HAADF-STEM image of fcc-2H-fcc Au-Cu CAH is shown, with a scale of 10 nm;

[0070] Figure 16C The definition of Cu domain thickness in fcc-2H-fcc Au-Cu CAH is shown;

[0071] Figure 16D Statistical analysis of Cu domain thickness in fcc-2H-fcc Au-Cu CAH is shown;

[0072] Figure 17 A spherical aberration-corrected high-resolution HAADF-STEM image of the Au / Cu interface in the fcc-2H-fcc Au-Cu CAH is shown.

[0073] Figure 18 HAADF-STEM image and corresponding EDS elemental mapping of a typical fcc-2H-fcc Au-Cu CAH are shown;

[0074] Figure 19 Shown along

[110] h /

[101] f Crystal model of the obtained fcc-2H-fcc Au-Cu CAH observed by zone axis;

[0075] Figure 20A TEM images of fcc-2H-fcc Au-Cu CSNs are shown, with a scale of 50 nm;

[0076] Figure 20B HAADF-STEM image of fcc-2H-fcc Au-Cu CSN is shown, with a scale of 10 nm;

[0077] Figure 20C The definition of Cu domain thickness in fcc-2H-fcc Au-Cu CSN is shown;

[0078] Figure 20D Statistical analysis of Cu domain thickness in fcc-2H-fcc Au-Cu CSNs is shown;

[0079] Figure 21 Spherical aberration-corrected high-resolution HAADF-STEM image of the Au / Cu interface in the fcc-2H-fcc Au-Cu CSN is shown;

[0080] Figure 22 HAADF-STEM image and corresponding EDS elemental mapping of a typical fcc-2H-fcc Au-Cu CSN are shown;

[0081] Figure 23 Shown along

[110] h /

[101] f Crystal model of the obtained fcc-2H-fcc Au-Cu CSN observed by zone axis;

[0082] Figure 24 The XRD pattern of the as-synthesized fcc-2H-fcc Au-Cu heterostructure is shown; the characteristic peak of the 2H phase, i.e., (100) marked by the black arrow h and (101) h , which is well presented in the XRD pattern;

[0083] Figure 25A Figure 2 shows the chemical state analysis of the as-synthesized fcc-2H-fcc Au-Cu heterostructures by XPS. The XPS spectrum of the Au 4f doublet indicates the metallic state of Au in the as-synthesized fcc-2H-fcc Au-Cu heterostructures.

[0084] Figure 25B Figure 2 shows the chemical state analysis of the as-synthesized fcc-2H-fcc Au-Cu heterostructures by XPS. The XPS spectrum of the Cu 2p doublet indicates the metallic state of Au and Cu in the as-synthesized fcc-2H-fcc Au-Cu heterostructures.

[0085] Figure 26A Shown are the normalized XANES spectra of Cu K-edge in as-prepared fcc-2H-fcc Au-Cu heterostructures, CuO, Cu2O, and Cu foil;

[0086] Figure 26B Fourier transforms of the Cu K-edge EXAFS spectra of fcc-2H-fcc Au-Cu heterostructures, CuO, Cu2O, and Cu foil are shown;

[0087] Figure 27A Shown is the corresponding Figure 26B k at the Cu K-edge of the Cu foil 2 Fitting results of weighted R space;

[0088] Figure 27B Shown is the corresponding Figure 26B k at the Cu K-edge of fcc-2H-fcc Au-Cu JNS 2 Fitting results of weighted R space;

[0089] Figure 27C Shown is the corresponding Figure 26B k at the Cu K-edge of the fcc-fcc-2H-fcc Au-Cu CAH 2 Fitting results of weighted R space;

[0090] Figure 27D Shown is the corresponding Figure 26B k at the Cu K-edge of the fcc-fcc-2H-fcc Au-Cu CSN 2 Fitting results of weighted R space;

[0091] Figure 28 is a summary corresponding to Figures 27A to 27D Table showing the fitting results of the Cu K-edge EXAFS spectra of Cu foil, fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CAH, and fcc-2H-fcc Au-Cu CSN;

[0092] Figure 29 Normalized XANES spectra of Au L3-edge in fcc-2H-fcc Au-Cu heterostructures, fcc-2H-fcc Au NRs, and Au foils are shown;

[0093] Figure 30 Fourier transforms of the Au L3-edge EXAFS spectra of fcc-2H-fcc Au-Cu heteronanostructures, fcc-2H-fcc Au NRs, and Au foil are shown;

[0094] Figure 31A Shown is the corresponding Figure 30 The k value at the Au L3 edge of the Au foil 2 Fitting results of weighted R space;

[0095] Figure 31B Shown is the corresponding Figure 30 k at the Au L3 edge of the fcc-2H-fcc Au NR 2 Fitting results of weighted R space;

[0096] Figure 31C Shown is the corresponding Figure 30 k at the Au L3 edge of the fcc-2H-fcc Au-Cu CAH 2 Fitting results of weighted R space;

[0097] Figure 31D Shown is the corresponding Figure 30 k at the Au L3 edge of the fcc-2H-fcc Au-Cu CAH 2 Fitting results of weighted R space;

[0098] Figure 31E Shown is the corresponding Figure 30 k at the Au L3 edge of the fcc-2H-fcc Au-Cu CSN 2 Fitting results of weighted R space;

[0099] Figure 32 is a summary corresponding to Figures 31A to 31E Table showing the fitting results of the Au L3-edge EXAFS spectra of Au foil, fcc-2H-fcc Au NR, fcc-2H-fcc Au-CuJNS, fcc-2H-fcc Au-Cu CAH, and fcc-2H-fcc Au-Cu CSN;

[0100] Figure 33 Wavelet transform of Cu K-edge EXAFS spectra of fcc-2H-fcc Au-Cu heterostructure and Cu foil (left) and fcc-2H-fcc Au-Cu heterostructure and Au foil (right) are shown;

[0101] Figure 34A TEM images of commercial fcc Cu NPs are shown, with a scale of 100 nm;

[0102] Figure 34B TEM images of commercial fcc Cu NPs are shown, with a scale of 20 nm;

[0103] Figure 34C Shown is the selected area electron diffraction (SAED) pattern of commercial fcc Cu NPs;

[0104] Figure 34D shows the XRD pattern of commercial fcc Cu NPs;

[0105] Figure 35An EDS spectrum is shown, which illustrates the composition of the Au+Cu mixture, wherein the Au / Cu atomic ratio is 46.70 / 53.30, which is close to the Au / Cu atomic ratio of fcc-2H-fcc Au-Cu JNS (47.38 / 52.62);

[0106] Figure 36A FE of the main CO2 reduction products obtained on fcc-2H-fcc Au-Cu JNS is shown;

[0107] Figure 36B FE of the main CO2 reduction products obtained on fcc-2H-fcc Au-Cu CAH is shown;

[0108] Figure 36C FE of the main CO2 reduction products obtained on fcc-2H-fcc Au-Cu CSN is shown;

[0109] Figure 37A Shown is the corresponding Figure 36A Detailed CO2RR performance of fcc-2H-fcc Au-Cu JNS. FE of all CO2RR products when using fcc-2H-fcc Au-Cu JNS as catalyst;

[0110] Figure 37B Shown is the corresponding Figure 36B Detailed CO2RR performance of fcc-2H-fcc Au-Cu CAH. FE of all CO2RR products when using fcc-2H-fcc Au-Cu CAH as catalyst;

[0111] Figure 37C Shown is the corresponding Figure 36B Detailed CO2RR performance of fcc-2H-fcc Au-Cu CSN. FE of all CO2RR products when using fcc-2H-fcc Au-Cu CSN as catalyst;

[0112] Figure 38 The CO2RR performance of commercial fcc Cu NPs is shown. FE of the main CO2RR products obtained on commercial fcc Cu NPs at different potentials;

[0113] Figure 39 The CO2RR performance of the Au+Cu mixture is shown. FE of the main CO2RR products obtained on the Au+Cu mixture at different potentials;

[0114] Figure 40Figure 2 shows the CO2RR performance of fcc-2H-fcc Au NRs. FE of the main CO2RR products obtained on fcc-2H-fcc Au NRs at different potentials.

[0115] Figure 41A The cathode energy efficiency of C2H4 on fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CAH, fcc-2H-fcc Au-Cu CSN, commercial fcc Cu NP and Au+Cu mixture at different potentials is shown. It should be noted that the cathode energy efficiency (CEE) of C2H4 is calculated by combining CO2RR with anodic oxygen evolution reaction. Coupling, using the equation CEE C2H4 =(E ox -E red . ) / (E ox -E red )×FE C2H4 Calculated. Here, E red and E ox are the thermodynamic potentials of CO2RR to C2H4 (0.08 V relative to RHE) and oxygen evolution reaction (1.23 V relative to RHE), respectively. red and E ox are the applied potentials in the cathode and anode of the H-type cell, respectively. For the calculation of the half-cell CEE, it is assumed that the anodic reaction occurs at an overpotential of 0 V, i.e., E ox =1.23 V (relative to RHE);

[0116] Figure 41B LSV curves of fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CAH, fcc-2H-fcc Au-CuCSN, and commercial fcc Cu NPs are shown to compare their electrocatalytic activities in CO2RR.

[0117] Figure 42 The C growth on fcc-2H-fcc Au-Cu heterostructures, commercial fccCu NPs, and Au+Cu mixtures at -1.1 V (vs. RHE) is shown. 2+ Comparison of the product and FE of C2H4;

[0118] Figure 43A Table comparing the CO2RR performance of the fcc-2H-fcc Au-Cu heterojunction nanostructures in this study and reported Cu-based catalysts in H-type cells;

[0119] Figure 43B corresponds to Figure 43ATable comparing the CO2RR performance of the fcc-2H-fcc Au-Cu heterostructures in this study and reported Cu-based catalysts in H-type cells;

[0120] Figure 43C corresponds to Figure 43A and 43B Table comparing the CO2RR performance of the fcc-2H-fcc Au-Cu heteronanostructures in this study and previously reported Cu-based catalysts in H-type cells;

[0121] Figure 43D corresponds to Figures 43A to 43C Table comparing the CO2RR performance of the fcc-2H-fcc Au-Cu heteronanostructures in this study and previously reported Cu-based catalysts in H-type cells;

[0122] Figure 44 The CO2RR for C 2+ Comparison of the partial current density of the products. C obtained on fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CAH, fcc-2H-fcc Au-Cu CSN and commercial fcc Cu NPs. 2+ partial current density of the product;

[0123] Figure 45 The C content of fcc-2H-fcc Au-Cu heterostructures, commercial fcc Cu NPs, and Au+Cu mixtures at different potentials is shown. 2+ Comparison of / C1 product ratio;

[0124] Figure 46 The catalytic performance comparison of this study with reported catalysts with similar heterogeneous structures for CO2RR in four aspects is shown;

[0125] Figure 47 Long-term catalytic stability evaluation of fcc-2H-fcc Au-Cu JNS at a constant potential of −1.1 V (vs. RHE) is shown. Vertical arrows pointing downward: electrolyte is refreshed at these points;

[0126] Figure 48A TEM image of fcc-2H-fcc Au-Cu JNS after 10 h of CO2 electrolysis is shown. The white arrows in this figure indicate that fcc-2H-fcc Au-Cu JNS can largely maintain their morphology and Janus nanostructure;

[0127] Figure 48BComposition evaluation of fcc-2H-fcc Au-Cu JNS after 10 h CO2RR test is shown;

[0128] Figure 49 HRTEM images of the Au / Cu interface in fcc-2H-fcc Au-Cu JNS after durability testing are shown, where (B) to (G) correspond to the fast Fourier transform (FFT) images of the selected areas marked in (A);

[0129] Figure 50A The flow cell performance of fcc-2H-fcc Au-Cu JNS is shown: C2H4 and C 2+ FE and C of the product 2+ partial current density of the product;

[0130] Figure 50B The total current density of fcc-2H-fcc Au-Cu JNS in the flow cell at different potentials is shown;

[0131] Figure 50C The specific FEs of all CO2RR products of fcc-2H-fcc Au-Cu JNS at different potentials in the flow cell are shown;

[0132] Figure 51 is a table comparing the intermediates and corresponding band positions detected by in situ ATR-FTIR spectroscopy of CO2RR from this study and reported studies;

[0133] Figure 52A In situ ATR-FTIR spectra of fcc-2H-fcc Au-Cu JNS under CO2RR conditions are shown;

[0134] Figure 52B In situ ATR-FTIR spectra of commercial fcc Cu NPs under CO2RR conditions are shown;

[0135] Figure 52C shows the in situ ATR-FTIR spectrum of Au+Cu mixture under CO2RR conditions;

[0136] Figure 53A In situ DEMS spectra of C2H4 production in CO2RR on fcc-2H-fcc Au-Cu JNS, commercial fcc Cu NPs, and Au+Cu mixtures are shown;

[0137] Figure 53B In situ DEMS spectra of CO production in CO2RR on fcc-2H-fcc Au-Cu JNS, commercial fcc Cu NPs, and Au+Cu mixtures are shown.

[0138] Figure 53C In situ DEMS spectra of H2 obtained on fcc-2H-fcc Au-Cu JNS, commercial fcc Cu NPs, and Au+Cu mixtures are shown;

[0139] Figure 53D In situ DEMS spectra of CH4 obtained on fcc-2H-fcc Au-Cu JNS, commercial fcc Cu NPs, and Au+Cu mixtures are shown;

[0140] Figure 54A The electron distribution of bonding orbitals and antibonding orbitals near the Fermi level in 2H / fcc Au-Cu JNS is shown. Red spheres = Cu; yellow spheres = Au; blue isosurfaces = bonding orbitals; green isosurfaces = antibonding orbitals;

[0141] Figure 54B The electron distribution of bonding and antibonding orbitals near the Fermi level in fcc Au-Cu JNS is shown. Red spheres = Cu; yellow spheres = Au; blue isosurfaces = bonding orbitals; green isosurfaces = antibonding orbitals;

[0142] Figure 55A The PDOS of 2H / fcc Au-Cu JNS is shown;

[0143] Figure 55B The PDOS of fcc Au-Cu JNS is shown;

[0144] Figure 56A The site-dependent PDOS of Cu-3d is shown;

[0145] Figure 56B The site-dependent PDOS of Au-5d is shown;

[0146] Figure 57 A comparison of d-band centers is shown;

[0147] Figure 58 A comparison of the PDOS of key intermediates for C2H4 generation is shown;

[0148] Figure 59 The adsorption energy of CO2 is shown;

[0149] Figure 60 The adsorption energy of CO* at different positions is shown;

[0150] Figure 61 The reaction energies of CC coupling on 2H Au-Cu and fcc Au-Cu are shown; and

[0151] Figure 62 The reaction energies for the formation of C2H4 on 2H Au-Cu and fcc Au-Cu are shown. DETAILED DESCRIPTION

[0152] As used herein, the forms "a", "an" and "the" are intended to include both the singular and the plural, unless the context clearly indicates otherwise.

[0153] As used herein, the words "example" or "exemplary" are intended to serve as examples, instances, or illustrations. Any aspect or design described in this disclosure as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, the use of the words "example" or "exemplary" is intended to present concepts in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or the context dictates, "X employs A or B" is intended to mean any natural inclusive permutation. That is, if X employs A, X employs B, or X employs both A and B, then "X employs A or B" holds true in any of the foregoing cases.

[0154] As used herein, the phrase "about" is intended to refer to values that vary slightly from the values recited herein.Examples have been described throughout this disclosure.

[0155] Without wishing to be bound by theory, the inventors, through their own research, trials and experiments, have devised a method for achieving site-selective growth of unconventional heterogeneous Cu (such as fcc-2H-fccCu) on unconventional heterogeneous Au nanostructures (such as fcc-2H-fcc Au nanorods (NR)) by precisely controlling the reduction kinetics and surfactant and concentration depletion strategies. Specifically, it is believed that the heterogeneous nanomaterials of the present invention can diversify the CO* adsorption configurations and reduce C 2+ In addition, due to the electronic modulation induced by the 2H phase, the heterogeneous nanomaterials of the present invention can have improved electroactivity of Au and Cu sites, resulting in stronger adsorption of CO2 and CO, and thus improving CO2 electroreduction performance.

[0156] In some exemplary embodiments, the heterogeneous nanomaterials of the present invention have a low ionization temperature at -1.1 V (vs. reversible hydrogen electrode (RHE)) for ethylene (C2H4) and C 2+ The products can exhibit Faradaic efficiency (FE) of 50.2% to 55.5% and 70.3% to 84.3%, respectively. In some specific embodiments, the heterogeneous nanomaterials of the present invention can also be C in the flow cell. 2+ Produced and delivered 220.80 mA cm -2 The industrially relevant part current density and FE of 61.3% are obtained.

[0157] In a first aspect of the present invention, there is provided a nanomaterial comprising: an Au nanostructure; and a Cu nanostructure provided with the Au nanostructure; wherein each of the Au nanostructure and the Cu nanostructure is in a different phase.

[0158] In some embodiments, the Cu nanostructures may be provided on and above the Au nanostructures. In some embodiments, the Cu nanostructures may be provided on and above the Au nanostructures and not fused with the Au nanostructures. In some embodiments, the Cu nanostructures may be epitaxially grown on the Au nanostructures without merging with the Au nanostructures. Specifically, the Au nanostructures and the Cu nanostructures are both in the form of fcc-2H-fcc heterogeneous structures. Without wishing to be bound by theory, in the case of the aforementioned structural arrangement / configuration, the Cu nanostructures and the Au nanostructures may thus form a tandem catalyst for the electrochemical CO2 reduction reaction (CO2RR), and the unconventional 2H phase of the Au nanostructures and the Cu nanostructures may enhance the *CO / CO spillover efficiency, thereby promoting the C in CO2RR. 2+ Therefore, the nanomaterials of the present invention can have excellent CO2RR performance, which will be explained in the later part of this disclosure.

[0159] In some embodiments, the Cu nanostructures can cover a first portion of the Au nanostructures. In some specific embodiments, the Au nanostructures can have a second portion covered by a surfactant.

[0160] The Au nanostructures can be provided in various forms, such as nanoparticles, nanobars, nanorods, nanotubes, nanowires, nanobelts, nanofilms, nanosheets, nanoplates, nanoflakes, etc. In some specific embodiments, the Au nanostructures can be in the form of Au nanorods, particularly in the form of heterogeneous Au nanorods, and more particularly in the form of fcc-2H-fcc Au nanorods.

[0161] In an embodiment in which the Au nanostructure is in the form of a fcc-2H-fcc Au nanorod, a first portion of the nanorod may be covered by a fcc-2H-fcc Cu nanostructure. Specifically, the fcc-2H-fcc Au nanorod and the fcc-2H-fcc Cu nanostructure may be arranged in a substantially lattice-matched manner, or in other words, the fcc-2H-fcc Au nanorod and the fcc-2H-fcc Cu nanostructure are substantially lattice-matched. As used herein, the phrase "substantially lattice-matching" or "substantially lattice-matched" describes that the arrangement of the fcc-2H-fcc Au nanorod and the fcc-2H-fcc Cu nanostructure is in a manner that their lattice parameters are substantially similar. For example, the unit cell of the 2H Cu of the fcc-2H-fcc Cu nanostructure may have a lattice parameter of approximately to about The lattice spacing of fcc-2H-fcc Au nanorods can be about to about lattice spacing.

[0162] In some embodiments, the Au nanorod may also include a second portion that is at least partially covered by a surfactant. Specifically, without wishing to be bound by theory, it is believed that the surfactant can be adsorbed and covered on the surface of the Au nanorod. Any initial Cu atom (i.e., Cu seed) deposited at the specific position of the Au nanorod will replace the surfactant or cause the surfactant to separate from the Au nanorod. In other words, any site / part of the Au nanorod provided / deposited / grown with Cu seed or Cu nanostructure will not be covered by the surfactant, while any site / part of the Au nanorod without Cu seed or Cu nanostructure will be covered by the surfactant. In some embodiments, the surfactant can be any one of oleylamine and dodecylamine.

[0163] In some embodiments, fcc-2H-fcc Au nanostructures, such as fcc-2H-fcc Au nanorods and fcc-2H-fcc Cu nanostructures, can be arranged in the form of Janus nanostructures. In these embodiments, the fcc-2H-fcc Cu nanostructures can be arranged on and above the longitudinal sides of the fcc-2H-fcc Au nanostructures, thereby forming an asymmetric nanostructure / nanomaterial.

[0164] In some embodiments, a first portion of the fcc-2H-fcc Au nanorod is circumferentially covered by a fcc-2H-fcc Cu nanostructure. In these embodiments, for example, the first portion may be arranged between two second portions on the fcc-2H-fcc Au nanorod, and at least one of the two second portions may be at least partially covered by a surfactant as described herein. Specifically, at least one of the two second portions may be at least partially covered by fcc Cu atoms of the fcc-2H-fcc Cu nanostructure. However, specifically, in these embodiments, any site / portion of the Au nanorod provided / deposited / grown with a Cu seed or Cu nanostructure is not covered by the surfactant, while any site / portion of the Au nanorod without a Cu seed or Cu nanostructure is covered by the surfactant. In these embodiments, the fcc-2H-fcc Au nanorod and the fcc-2H-fcc Cu nanostructure are arranged in the form of a coaxial heterogeneous nanostructure.

[0165] In some embodiments, the fcc-2H-fcc Au nanorods may be encapsulated by fcc-2H-fcc Cu nanostructures. In these embodiments, the fcc-2H-fcc Au nanorods and fcc-2H-fcc Cu nanostructures are arranged in the form of fcc-2H-fcc Au-Cu core-shell nanostructures.

[0166] Methods for preparing the nanomaterials described herein will now be disclosed. The methods described herein may be seeded growth methods. Without wishing to be bound by theory, it is believed that seeded growth methods may have better product control than synthesis methods involving one-step synthesis (such as wet chemical synthesis). In other words, seeded growth methods may more easily obtain the desired seeded growth product than synthesis methods involving one-step synthesis (such as wet chemical synthesis). The methods described herein may include the following steps: a) providing a reaction mixture comprising fcc-2H-fcc Au nanostructures, a reducing agent, and a copper precursor; b) heating the reaction mixture for a predetermined time, followed by cooling the reaction mixture to room temperature; c) isolating the nanomaterial from the reaction mixture.

[0167] In some embodiments, the reaction mixture may further comprise a surfactant as described herein, and the fcc-2H-fcc Au nanostructures may be provided in the form of fcc-2H-fcc Au nanorods. In these embodiments, the reaction mixture may be provided by adding a copper precursor at a predetermined rate to a solution mixture comprising fcc-2H-fcc Au nanostructures (such as fcc-2H-fcc Au nanorods as described herein), a surfactant as described herein, and a reducing agent at an elevated temperature.

[0168] Specifically, it is believed that surfactants can promote the dispersion of Au nanostructures, thereby minimizing the chance of Au nanostructure aggregation. Additionally, without wishing to be bound by theory, the inventors have devised that surfactants can play a role in modulating the reduction kinetics of the reducing agent acting on the Au nanostructures during synthesis, thereby producing the various forms of nanostructured products described herein. For example, in some embodiments, the placement of Cu atoms can be hindered by surfactants, resulting in asymmetric nanostructures in the final product.

[0169] In some embodiments, the surfactant may include a mixture of oleylamine and dodecylamine. In some exemplary embodiments, the volume ratio of oleylamine to dodecylamine may be approximately 2:3, such as 1.75:3, 1.78:3, 1.8:3, 1.85:3, 1.9:3, 1.94:3, 1.98:3, 2:3, 2.01:3, 2.1:3, 1.76:3.01, 1.82:3.1, 1.96:3.02, 2:3.05, and the like. Optionally or additionally, dodecylamine may be replaced by a derivative thereof, such as hexadecylamine, octadecylamine, and the like. In some exemplary embodiments, the copper precursor may include copper acetylacetonate. In some exemplary embodiments, the reducing agent may include any one of 1,2-hexanediol, 1,2-hexanediol, and 1,2-butanediol.

[0170] Without wishing to be bound by theory, it is believed that by controlling the supply rate of Cu atoms (from a Cu precursor) to the solution mixture, various forms of nanostructures as described herein can be produced. For example, it is believed that when the Cu atom supply rate is very high (e.g., 1.40 mL min -1 or higher), the oversupplied Cu atoms can completely cover the seeded Cu atoms in a short time, thereby essentially producing Au@Cu core-shell nanostructures. On the contrary, it is also believed that when the Cu atom supply rate is very slow (e.g., 0.062 mL min -1 or lower), the Cu atomic concentration may be insufficient to nucleate before the Au nanostructures (such as Au nanorods) aggregate together or sink, resulting in the nanomaterial having the Au nanostructure being partially covered by the Cu nanostructure.

[0171] Thus, in some embodiments, when the reducing agent comprises 1,2-hexanediol, the copper precursor may be heated at a rate of about 0.094 mL / min. -1 (such as from 0.088 mL min -1 to 0.12 mL min -1 ) is added to the solution mixture at a rate of . In these embodiments, it can produce Au-Cu Janus nanostructures as described herein.

[0172] In some other embodiments, when the reducing agent comprises 1,2-hexadecanediol, the copper precursor may be heated at a rate of about 0.062 mL min -1 (such as from 0.056 mL min -1 to 0.07 mL min -1 ) is added to the solution mixture at a rate of . In these embodiments, it can produce Au-Cu coaxial heterogeneous nanostructures as described herein.

[0173] In yet other embodiments, when the reducing agent comprises 1,2-butanediol, the copper precursor may be added at a rate of about 0.5 mL / min. -1 (such as from 0.2 mL min -1 to 1 mL min -1 ) is added to the solution mixture at a rate of . In these embodiments, it can produce Au-Cu core-shell nanostructures as described herein.

[0174] In some embodiments, the copper precursor may be added to the solution mixture at a temperature of about 110° C. to about 130° C., such as 108° C. to 130° C., 109° C. to 130° C., 108° C. to 132° C., 110° C. to 132° C., 112° C. to 130° C., 112° C. to 128° C., 115° C. to 125° C., 118° C. to 122° C., etc. In some example embodiments, the copper precursor may be added to the solution mixture at a temperature of about 120° C.

[0175] The solution mixture can be prepared by isolating the fcc-2H-fcc Au nanostructures from a stock solution of the fcc-2H-fcc Au nanostructures, such as by centrifugation, followed by the addition of a surfactant, such as about 200 μL, and then adding a reducing agent as described herein to the isolated fcc-2H-fcc Au nanostructures. Optionally or additionally, the solution mixture can be repeatedly sonicated to improve the homogeneity of the solution mixture.

[0176] In step b), the reaction mixture may be heated at a temperature of about 120° C. for about 2 min, for example, and then the reaction mixture may be cooled to room temperature, such as by means of an ice bath.

[0177] In step c), in some exemplary embodiments, the nanomaterial as described herein can be separated from the reaction mixture by washing the nanomaterial with a suitable solvent (such as n-hexane). Optionally or additionally, the washing step can be repeated as needed. Optionally or additionally, the separated nanomaterial can be stored in a suitable liquid medium, particularly an inert liquid medium (such as n-hexane) at a reduced temperature (such as about -4°C to about 4°C).

[0178] Hereinafter, the present invention is described in more detail by way of examples, but the present invention is not limited thereto.

[0179] Example

[0180] Material

[0181] Potassium gold(III) chloride (KAuCl4, 98%), Nafion (117 solution, 5 wt%), and commercial fcc Cu NPs (approximately 50 nm in size) were purchased from Sigma-Aldrich. Oleylamine (OAM, 80–90%), dodecylamine (DDA, 98%), 1,2-butanediol (BDO, >98% (GC)), 1,2-hexanediol (HDO, 98%), 1,2-hexadecanediol (HDD, 98%), copper acetylacetonate (Cu(acac)2, 97%), isopropyl alcohol (IPA, AR, ≥99.5%), cyclohexane (>99%), and ethylene glycol (EG, >99% (GC)) were purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd. Ethanol (ACS grade, very pure) and n-hexane (ACS grade, 99%) were purchased from Anaqua Global International Inc. Limited. Oxygen and CO2 gases were purchased from Specialty Gas Engineering Company Limited. All chemical reagents and materials were used as received without any further purification. Deionized (DI) water with a resistance of 18.2 MΩcm was used in the experiments.

[0182] Characterization

[0183] TEM images were collected on a FEI Tecnai T12TEM operated at 120 kV. High-resolution TEM (HRTEM) images were taken on a JEOL 2100F operated at 200 kV. Spherical aberration-corrected HAADF-STEM images and EDS elemental mapping were obtained by a JEOL ARM200F operated at 200 kV with a cold field emission gun and a double hexapole Cs corrector (CEOS GmbH). Scanning electron microscopy (SEM) images were obtained by a Thermo Scientific Quattro S operated at 20 kV. XRD patterns were obtained by X-ray diffraction with Cu Kα radiation. The XPS measurements were performed on a VG ESCALAB 220i-XL surface analysis system with a basic vacuum of less than 10 -9XAS measurements were performed in transmission mode at beamline 1W1B at the Beijing Synchrotron Radiation Facility. Data were processed using the Athena and Artemis software packages. The Cu loading was confirmed by inductively coupled plasma optical emission spectroscopy (ICP-OES, PerkinElmer, Optima 8000).

[0184] Preparation of working electrode for electrochemical CO2RR measurement in H-type cell

[0185] The newly synthesized heterogeneous nanostructure (or catalyst) was first transferred from n-hexane to ethanol by gradually changing the volume ratio between n-hexane and ethanol during centrifugal washing. Specifically, the catalyst was washed with a mixture of n-hexane and ethanol in a ratio of 6:1 (v / v), 6:6 (v / v) and 1:6 (v / v), and finally washed with pure ethanol. After washing with pure ethanol, the catalyst was redispersed in ethanol. At this stage, the transfer of the catalyst from n-hexane to ethanol was completed. After measuring the concentration of Cu and / or Au by ICP-OES, an appropriate amount of catalyst stock solution was centrifuged. Specifically, as used herein, the phrase "appropriate amount" refers to 100 μg of Cu when the sample is pure fcc Cu NP, fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CHS, fcc-2H-fcc Au-CuCSN or Au+Cu mixture; and when the sample is pure fcc-2H-fcc Au NR, this phrase refers to 100 μg of Au. The obtained precipitate was redispersed in 96 μL of ethanol, followed by the addition of 4 μL of Nafion solution (5 wt%) and subsequent sonication for 5 min to prepare a uniform catalyst ink. 30 μL of the catalyst ink was then dropped onto a 5 mm diameter glassy carbon electrode (GCE) containing 30 μg of Cu. Note that for the test of fcc-2H-fcc Au NR, the Au loading on each electrode was also 30 μg. After the electrode dried, the initially prepared working electrode was stored in a vacuum oven before the electrocatalytic test.

[0186] CO2RR testing in H-type cells

[0187] All electrochemical measurements were performed using an Ivium-n-Stat electrochemical workstation in a three-electrode system. The catalysts were tested in a gas-tight, two-chamber H-type cell separated by an ion exchange membrane (Nafion 212). A 0.1 M KHCO3 aqueous solution saturated with CO2 was used as the electrolyte. Typically, both the anode and cathode chambers were filled with 8 mL of electrolyte. A catalyst-modified GCE, an Ag / AgCl electrode (filled with saturated KCl solution), and a Pt plate were used as the working electrode, reference electrode, and counter electrode, respectively. The applied potentials were converted to the RHE scale based on the equation E (relative to RHE) = E (relative to Ag / AgCl) + 0.197 + 0.0591 × pH. Unless otherwise stated, all applied potentials in this study were recorded with 85% solution resistance correction.

[0188] Before the test, CO2 gas (99.999%, Specialty Gas Engineering Company Limited) was blown into the 0.1M KHCO3 aqueous solution in the cathode chamber for 30 minutes. During the test, CO2 gas was continuously blown into the 0.1M KHCO3 aqueous solution in the cathode chamber at a flow rate of 20 standard cubic centimeters per minute (sccm). The gaseous products of CO2RR were analyzed by directly connecting the gas outlet of the cathode chamber to an online gas chromatograph (GC, Agilent Technologies 7890B), which was equipped with two flame ionization detectors (FID) and a thermal conductivity detector (TCD). After CO2 electrolysis for 1 hour, the liquid products in the cathode electrolyte were collected and analyzed by 1 The samples were analyzed using a H nuclear magnetic resonance (NMR) spectrometer (Bruker AVANCE III HD, 300 MHz).

[0189] Electrochemical CO2RR measurements in a flow cell

[0190] Preparation of working electrode

[0191] Typically, 3 mg of catalyst was added to 1 mL of ethanol, followed by the addition of 25 μL of Nafion solution (5 wt%), and then sonicated for 5 min to form a uniform catalyst ink. Afterwards, 0.83 mL of the catalyst ink was dropped onto a gas diffusion electrode (GDE; size: 1.0 cm × 2.5 cm, Sigracet 29BC) to ensure a catalyst loading of 1.0 mg cm -2 The catalyst-modified GDE was naturally dried and stored in a vacuum oven for further use.

[0192] CO2RR testing in a flow cell

[0193] Electrochemical CO2RR measurements were performed in a three-channel flow cell consisting of an anode chamber, a cathode chamber, and a CO2 gas flow field. An anion exchange membrane (Fumasep, FAA-3-PK-130) was used to separate the anode and cathode chambers. Catalyst-modified GDE, saturated Ag / AgCl, and Ni foam were used as working, reference, and counter electrodes, respectively. 1.0 M KOH solution was used as the anolyte and catholyte. The electrolytes in the cathode and anode chambers were circulated independently by a dual-channel peristaltic pump (LongerPump, BT100-2J) at a flow rate of 10 mL min -1 High purity CO2 gas (99.999%, Specialty Gas Engineering Company Limited) was continuously passed through the CO2 flow field behind the GDE at a flow rate of 5 sccm. The gaseous product and liquid product were respectively measured by online GC and 1 Analyses were performed using a H NMR spectrometer. Note that no solution resistance correction (IR correction) was performed to accurately reflect the potential applied between the reference electrode and the working electrode in the flow cell.

[0194] In situ ATR-FTIR characterization

[0195] In situ ATR-FTIR measurements were performed in absorption mode on a Nicolet iS50 IR spectrometer equipped with a mercury cadmium telluride (MCT) detector cooled by liquid nitrogen. A catalyst-loaded Au-coated Si hemispherical prism (20 mm diameter, MTI) was used as the working electrode. ATR-FTIR spectra were acquired at 8 cm -1 The scan rate was 5 mV s -1 The exposure time for each spectrum was 10 s. All spectra were background subtracted.

[0196] In situ DEMS characterization

[0197] In situ DEMS measurements were performed on a Linglu DEMS system. -1 Signals were collected during a linear sweep of the working electrode from 0 to -1.3 V (vs. RHE) at a scan rate of 100 Å. A homemade electrochemical cell was used for the experiments. Catalyst-modified GCE, Pt wire, and saturated Ag / AgCl were used as the working, counter, and reference electrodes, respectively.

[0198] Calculation Settings

[0199] All theoretical calculations were performed using density functional theory (DFT) embedded in the CASTEP package to reveal the effects of the 2H phase. Specifically, the generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) were applied to ensure an accurate description of the exchange-correlation interaction in electrocatalysis. The plane wave basis cutoff energy was set to 440 eV by the choice of ultrafine mass and ultrasoft pseudopotentials. At the same time, by balancing accuracy and efficiency, we adopted a rough mass K-point set and the Broyden-Fletcher-Goldfarb-Shannon (BFGS) algorithm for all energy minimizations. We introduced a To ensure that the geometry optimization has enough space between periodic units. For all geometry optimizations, we apply a strict criterion where the Hellmann-Feynman force should not exceed And the total energy difference should not exceed 5×10 -5 eV / atom.

[0200] Example 1

[0201] Synthesis of fcc-2H-fcc Au NRs

[0202] The synthesis steps of fcc-2H-fcc Au NRs are as follows: DDA and OAM were first melted in an oven at 63°C for 30 min. Then, 2.4 mL of DDA and 1.6 mL of OAM were added to a 20 mL glass vial and vortexed continuously for 5 min to form a homogeneous solution. Thereafter, 6 mg of KAuCl4 was added to the above solution, followed by an oxygen purge for 15 min. Subsequently, the glass vial was immediately sealed. After sonication for approximately 5 min to form a homogeneous solution, the glass vial was placed in an oil bath at 63°C for 18 h. After the reaction, 4 mL of cyclohexane was added to the glass vial. The resulting mixture was sonicated for 3 min and then centrifuged at 5000 rpm for 6 min to obtain the product. Finally, the product was further washed five times with 6 mL of cyclohexane and then redispersed in 2 mL of cyclohexane for later use.

[0203] Example 2

[0204] Synthesis of Heterogeneous fcc-2H-fcc Au-Cu Janus Nanostructures (fcc-2H-fcc Au-Cu JNS)

[0205] To synthesize fcc-2H-fcc Au-Cu JNS, 2 mL of fcc-2H-fcc Au NR solution was first centrifuged and the supernatant was discarded, leaving only the precipitate. 200 μL of OAM / DDA mixture (v / v = 2 / 3) was then added to the centrifuge tube containing the Au NR precipitate, followed by sonication for 5 min to form a homogeneous solution. Subsequently, 1.1 mL of HDO was added to the above solution, followed by sonication again for 5 min. Thereafter, the resulting solution was transferred to a 4 mL glass vial and placed in an oil bath at 120 ° C under magnetic stirring, followed by immediate filtration using a syringe pump (New Era Pump Systems Inc.) at 0.094 mL min -1 0.25mL of Cu (acac) 2 solution (13.20mM in OAM) was injected at an injection speed of 1000 nm. After completing the injection, the resulting solution was reheated for 2 min and then rapidly cooled to room temperature with an ice bath. In order to collect the product, the resulting solution was first mixed with 4mL of n-hexane and centrifuged at 10,000 rpm for 3 min. The precipitate obtained was then further washed twice with n-hexane. Finally, the product was redispersed into 1mL of n-hexane and stored in a refrigerator for use.

[0206] Example 3

[0207] Synthesis of Heterogeneous fcc-2H-fcc Au-Cu Coaxial Heterogeneous Nanostructures (fcc-2H-fcc Au-Cu CAH)

[0208] To synthesize fcc-2H-fcc Au-Cu CAH, 2 mL of fcc-2H-fcc Au NR solution was first centrifuged and the supernatant was discarded, leaving only the precipitate. 200 μL of OAM / DDA mixture (v / v = 2 / 3) was then added to the centrifuge tube containing the Au NR precipitate, followed by sonication for 5 min to form a homogeneous solution. After the above solution was transferred to a 4 mL glass vial, 1.3 mL of HDD (pre-melted in an oven) was added and sonicated again for 5 min. The resulting solution was then placed in an oil bath at 120 ° C under magnetic stirring and immediately added using a syringe pump at 0.062 mL min -1 0.5mL of Cu(acac)2 solution (4.80mM in OAM) was injected at an injection speed of 1000 nm. After completing the injection, the resulting solution was heated for 10 min and then rapidly cooled to room temperature with an ice bath. In order to collect the product, the resulting solution was first mixed with 4mL of hot n-hexane and centrifuged at 10,000 rpm for 3 min. The precipitate obtained was then further washed twice with hot n-hexane. Finally, the product was redispersed into 1mL of n-hexane and stored in a refrigerator for subsequent use.

[0209] Example 4

[0210] Synthesis of Heterogeneous fcc-2H-fcc Au-Cu Core-Shell Nanostructures (fcc-2H-fcc Au-Cu CSNs)

[0211] To synthesize fcc-2H-fcc Au-Cu CSNs, 2 mL of the fcc-2H-fcc Au NR solution was first centrifuged, and the supernatant was discarded, leaving only the precipitate. 200 μL of an OAM / DDA mixture (v / v = 2 / 3) was then added to the centrifuge tube containing the Au NR precipitate, followed by sonication for 5 min to form a homogenous solution. Subsequently, 800 μL of HDO was added and sonicated again for 5 min. The resulting solution was transferred to a 4 mL glass vial and 0.75 mL of a Cu(acac)2 solution (8.00 mM in OAM) was added continuously via a pipette at one time. The vial was immediately placed in an oil bath at 160°C and heated under magnetic stirring for 15 min. To collect the product, the resulting solution was first mixed with 4 mL of n-hexane and centrifuged at 10,000 rpm for 3 min. The obtained precipitate was then further washed twice with n-hexane. Finally, the product was redispersed in 1 mL of n-hexane and stored in a refrigerator for later use.

[0212] Example 5

[0213] Synthesis and Structural Characterization of Heterogeneous fcc-2H-fcc Au-Cu Nanostructures

[0214] like Figure 1 As shown schematically, by using well-defined heterogeneous fcc-2H-fcc Au NRs as seeds, precisely tuning the reduction kinetics and concentration of copper acetylacetonate (Cu(acac)2), and selecting an appropriate surfactant, we achieved site-selective epitaxial growth of heterogeneous fcc-2H-fcc Cu. Specifically, the reduction kinetics of the Cu precursor were systematically controlled by selecting an appropriate reducing agent and a suitable injection rate of the Cu precursor.

[0215] Specifically, heterogeneous fcc-2H-fcc Au NRs were synthesized by reducing KAuCl4 in an OAM / DDA mixture (v / v = 2 / 3) solvent at 63 °C for 18 h. TEM images showed that the as-prepared Au NRs exhibited a high-purity rod-like morphology ( Figure 2A and 2B Statistical analysis of Au NRs showed that the heterogeneous fcc-2H-fcc Au NRs had a length of 32.57 ± 5.82 nm and a width of 15.05 ± 2.44 nm ( Figure 3A and 3B). HRTEM images confirmed that the two ends and the middle region of the Au NR exhibited fcc phase and 2H phase, respectively, forming a well-defined fcc-2H-fcc heterophase along the long axis ( Figure 4A ). Figure 4B The crystal model showing the phase distribution in the as-prepared Au NR is schematically presented. The XRD pattern further confirmed the fcc-2H-fcc heterogeneous phase of Au NR ( Figure 5 The XPS spectra of Au 4f doublets indicate that the metallic state of Au in these as-prepared Au NRs ( Figure 6 ).

[0216] For fcc-2H-fcc Au-Cu JNS, 1,2-hexanediol (HDO) was selected as the reducing agent and the HDO was prepared by a syringe pump at a rate of 0.094 mL min -1 Inject Cu(acac)2 solution to synthesize ( Figure 1 and 7 Transmission electron microscopy (TEM) and high-angle annular dark-field scanning TEM (HAADF-STEM) images of fcc-2H-fcc Au-Cu JNS revealed the separated distribution of Cu and Au domains within a single nanostructure, and the thickness of the Cu domain was approximately 7.48 ± 1.55 nm ( Figures 8A to 8D ).

[0217] Figure 9 Representative aberration-corrected HAADF-STEM images in Figure 3 probe the structure of fcc-2H-fcc Au-Cu JNS at the atomic scale, demonstrating the epitaxial growth of Cu domains on fcc-2H-fcc Au NRs. and The measured lattice spacings are consistent with the interplanar distances of the close-packed Cu and Au domains, respectively. Importantly, the central region of the Cu domain exhibits an "AB" stacking sequence along the close-packed direction, while the ends display a characteristic "ABC" stacking sequence, indicating an fcc-2H-fcc heterogeneous phase in the Cu domain. Similar structural features are also observed in the Au domain.

[0218] To further illustrate the phase distribution of Cu domains, Figure 10A and 10B The fcc phase and the 2H phase are schematically illustrated, in which the characteristic stacking sequence of close-packed planes is well presented, namely "ABC" for the fcc phase and "AB" for the 2H phase. HAADF-STEM images and corresponding energy-dispersive X-ray spectroscopy (EDS) elemental mapping show that Cu is deposited on one side of the Au NR, while the other areas of the Au NR are exposed ( Figure 12). HAADF-STEM tomographic reconstruction further confirmed the asymmetric Au-Cu heterostructure. Based on the above characterization, Figure 13 schematically shows a crystal model of Au-Cu JNS showing co-exposed fcc-2H-fcc Au and fcc-2H-fcc Cu.

[0219] It is believed that good dispersion of Au NRs, appropriate injection speed of Cu precursor, and suitable Cu(acac)2 concentration are all crucial for the successful synthesis of fcc-2H-fcc Au-Cu JNSs.

[0220] It is also believed that achieving good dispersion of fcc-2H-fcc Au NRs by selecting a suitable solvent is very important for the successful synthesis of fcc-2H-fccAu-Cu JNSs. Figure 13A As shown in Figure 3, if polar solvents such as EG are used, fcc-2H-fcc AuNRs cannot be well dispersed, resulting in the formation of large agglomerates of fcc-2H-fcc Au NRs. Therefore, although some fcc-2H-fcc Au-Cu JNS can be observed, there are always serious agglomerations in the final product ( Figure 13B ).

[0221] It is further believed that the effect of injection speed will affect the reduction kinetics of the synthesized fcc-2H-fcc Au-Cu JNS. To conduct such studies, the injection speed was changed from 0.094 mL min -1 Systematically tuned to 1.86 mL min -1 、1.40mL min -1 、0.064mL min -1 and 0.031 mL min -1 When the injection speed is too high, most of the Cu domains completely cover the fcc-2H-fccAu NR ( Figure 14A When the injection speed gradually decreases, the content of fcc-2H-fcc Au-Cu JNS gradually increases ( Figure 14B and 14C ). However, when the injection speed is too low, the Cu precursor is difficult to reduce. The above results show that a suitable injection speed is important for the successful synthesis of fcc-2H-fcc Au-Cu JNS ( Figure 14D ).

[0222] In addition, it is believed that the concentration of Cu precursor will also affect the synthesis of fcc-2H-fcc Au-Cu JNS. Therefore, the effect of Cu precursor concentration was studied by changing the Cu precursor concentration from 13.20 mM to 5.20 mM, 9.20 mM, 7.20 mM, and 20.40 mM, respectively. When the concentration of Cu precursor was as low as 5.20 mM, the Cu precursor could not be reduced, and no Cu growth occurred on fcc-2H-fcc Au NRs ( Figure 15A When the Cu concentration increased to 9.20 mM, some fcc-2H-fcc Au-Cu JNS appeared ( Figure 15B However, when the Cu concentration was increased up to 17.20 mM and 20.40 mM, respectively, the Cu domains in the final product completely covered the AuNRs in most cases ( Figure 15C and 15D The above results indicate that the appropriate concentration of Cu precursor is also important for the successful synthesis of fcc-2H-fcc Au-Cu JNS.

[0223] At the same time, 1,2-hexadecanediol (HDD) was selected as the reducing agent and injected into the mixture at a rate of 0.062 mL min -1 Inject Cu(acac)2 solution to synthesize fcc-2H-fcc Au-Cu CAH( Figure 1 and 7 ). TEM and STEM images reveal the size distribution and morphology of fcc-2H-fcc Au-Cu CAH, where the Cu domains have a thickness of approximately 7.20 ± 1.62 nm ( Figures 16A to 16D ). Figure 17 A representative aberration-corrected HAADF-STEM image of an fcc-2H-fcc Au-Cu CAH is shown, demonstrating epitaxial growth of Cu domains on fcc-2H-fcc Au NRs. Similarly, the Cu domains adopt an fcc-2H-fcc heterophase, as evidenced by the characteristic stacking sequence of "AB" in the middle region of the Cu domain and "ABC" at both ends. Meanwhile, the Au domains also maintain the fcc-2H-fcc heterophase. and The measured lattice spacing of is in good agreement with the interplanar distance of the close-packed planes of Cu and Au, respectively. HAADF-STEM images and corresponding EDS elemental mappings show that Cu is mainly deposited on the side of the Au NR, but rarely grows on the two tips of the Au NR, resulting in the selective exposure of Au at both ends of the resulting nanostructure ( Figure 18 Based on these observations, Figure 19 The crystal structure of a typical fcc-2H-fcc Au-Cu CAH is schematically depicted.

[0224] When 1,2-butanediol (BDO) was used as the reducing agent and the Cu(acac)2 solution was added via a pipette in one shot / one-batch, fcc-2H-fcc Au-Cu CSNs were obtained ( Figure 1 and Figures 20A to 20D ). Figure 21 Representative aberration-corrected HAADF-STEM images in Figure 3 demonstrate epitaxial growth of Cu on Au NRs. The characteristic stacking sequence in the middle region and at both ends of the Cu domains indicates their fcc-2H-fcc heterophase. and The measured lattice spacing is assigned to the interplanar distance of the close-packed planes of Cu and Au, respectively. HAADF-STEM images and EDS elemental mapping show that the Au core is completely covered by the Cu shell ( Figure 22 ). Taken together, Figure 23 A crystal model illustrating the fcc-2H-fcc core-shell structure of an Au-Cu CSN is shown.

[0225] Example 6

[0226] X-ray spectroscopy analysis of heterogeneous fcc-2H-fcc Au-Cu heterostructures

[0227] The structure of the as-prepared fcc-2H-fcc Au-Cu heterostructures was investigated using X-ray diffraction (XRD). Figure 24 After Cu is grown on Au NR, the characteristic peak of 2H Au, namely (100) h and (101) h , which is well preserved in the XRD pattern. In addition, the peak positions of Au and Cu do not show obvious shifts compared to the standard peak positions, which indicates that the phase separation of Au and Cu in the resulting heterogeneous nanostructures is well matched with the observations of TEM, STEM and EDS. X-ray photoelectron spectroscopy (XPS) core level spectra of Au 4f doublets and Cu 2p doublets indicate that the metallic state of Au and Cu in these fcc-2H-fcc Au-Cu nanostructures ( Figure 25A and 25B Meanwhile, the small satellite peaks in the Cu 2p XPS spectrum may originate from the slight oxidation of Cu in air.

[0228] X-ray absorption spectroscopy (XAS) was further used to investigate the electronic structure and coordination environment of the initially prepared fcc-2H-fcc Au-Cu heterostructures. In the Cu K-edge X-ray absorption near-edge structure (XANES) spectrum, the white line of the fcc-2H-fcc Au-Cu heterostructures was located between the Cu foil and Cu2O or CuO, and the spectrum of the heterostructures was more similar to that of the Cu foil ( Figure 26A ), indicating that the Cu domain is mainly in the metallic state, but the surface Cu atoms are slightly oxidized. In the Cu K-edge extended X-ray absorption fine structure (EXAFS) spectrum, about The main peak is attributed to the Cu-Cu scattering path ( Figure 26B The fitting results of Cu K-edge EXAFS spectra reveal that the Cu-Cu bonds in the as-prepared fcc-2H-fcc Au-Cu heterostructures and Cu foils have a Cu-Cu bond strength of approximately Similar bond lengths ( Figures 27A to 27D and Figure 28 ).

[0229] The Cu-Cu coordination numbers of fcc-2H-fcc Au-Cu JNS, CAH, and CSN are different, namely 3.8, 5.5, and 7.3, respectively, which is largely due to the variation in the Cu domain size in these heterogeneous nanostructures ( Figure 8B 、 16B and 20B). At the same time, the Cu-Cu coordination number in the initially prepared fcc-2H-fcc Au-Cu heterostructures is much larger than the corresponding Cu-O coordination number, further proving that metallic Cu is dominant. In the Au L3 edge XANES spectrum ( Figure 29 ), the white line position of the initially prepared fcc-2H-fcc Au-Cu heterostructures is similar to that of Au NR and Au foil, indicating that the Au domains in the three samples remain in the metallic state, which is consistent with the XPS results ( Figure 25A ).

[0230] In the Au L3 edge EXAFS spectrum ( Figure 30 ), in addition to the Au-Au scattering path, an Au-Cu scattering path also appears for the initially prepared fcc-2H-fcc Au-Cu heterostructures. Correspondingly, the fitting results of the Au L3-edge EXAFS spectra show that when the sample changes from Au-Cu JNS to Au-Cu CAH and Au-Cu CSN, the Au-Cu coordination number increases from 1.0 to 1.3 and 2.3 ( Figures 31A to 31E and Figure 32 ), indicating that more and more surface Au atoms are coordinated with Cu atoms in this order. This observation is consistent with the TEM results ( Figure 8A 、 16A The maximum wavelet transform (WT) intensity of the Cu K-edge EXAFS spectrum of the initially prepared fcc-2H-fcc Au-Cu heterostructure is very close to that of the Cu foil ( Figure 33, left), again confirming that metallic Cu dominates in all three samples. The intensity maxima of Au-Cu JNS, Au-Cu CAH, and Au-Cu CSN in the Au L3 edge WT are also similar to those of the Au foil, indicating the formation of Au-Cu bonds at the interface and the metallic state of most Au species ( Figure 33 , right side).

[0231] Example 7

[0232] Electrochemical CO2RR performance of heterogeneous fcc-2H-fcc Au-Cu heterostructures

[0233] The as-prepared fcc-2H-fcc Au-Cu heterostructures were applied as catalysts for electrochemical CO2RR. CO2 reduction measurements were first performed in an H-type cell using a 0.1 M potassium bicarbonate (KHCO3) aqueous solution as the electrolyte, with a catalyst-modified glassy carbon electrode, Ag / AgCl (in saturated KCl solution), and a Pt plate as the working, reference, and counter electrodes, respectively. As control samples, fcc-2H-fcc Au NRs and commercial fcc Cu nanoparticles (NPs; Figures 34A to 34D ) and physical mixtures of fcc-2H-fcc Au NRs and commercial fcc Cu NPs (denoted as Au+Cu mixture; Figure 35 ).

[0234] like Figures 36A to 36C and Figures 37A to 37C As shown, the as-prepared fcc-2H-fcc Au-Cu heterostructures with unconventional Cu phase exhibit excellent performance in CO2RR, showing more than 50% FE at their optimal potential. C2H4 Notably, fcc-2H-fcc Au-Cu JNS delivers the highest FE of 55.5% at −1.1 V (vs. RHE). C2H4 In contrast, commercial fcc Cu NPs and Au+Cu mixtures only exhibit the highest FE of 44.9% and 21.5% at −1.15 V (vs. RHE), respectively. C2H4 ( Figure 38 and 39 ). Under most applied potentials, the major product obtained on fcc-2H-fcc Au NRs was CO ( Figure 40 Meanwhile, fcc-2H-fcc Au-Cu JNS also showed a superior cathode energy efficiency (CEE) of 27.4% compared with other samples, especially at lower negative potentials ( Figure 41AMoreover, based on the linear sweep voltammetry curves, fcc-2H-fcc Au-Cu JNS also showed the highest current density compared with those of fcc-2H-fcc Au-Cu CAH, fcc-2H-fcc Au-Cu CSN, and commercial fcc Cu NPs ( Figure 41B ), indicating its outstanding electrocatalytic activity.

[0235] To better illustrate the differences in CO2RR performance among fcc-2H-fcc Au-Cu JNS, fcc-2H-fcc Au-Cu CAH, fcc-2H-fccAu-Cu CSN, commercial fcc Cu NPs, and Au+Cu mixtures, their CO2RR performance was compared. 2+ The product and FE of C2H4, and the result is as Figure 42 Importantly, in all these samples, the fcc-2H-fcc Au-Cu JNSs exhibited a high C 2+ The product and C2H4 showed the highest FE, i.e., 84.3% and 55.5%, respectively, which also made fcc-2H-fcc Au-Cu JNS one of the best reported Cu-based CO2RR catalysts ( Figures 43A to 43D ). In general, at -1.1 V (vs. RHE), the C 2+ The FE of the products and C2H4 has the following order: fcc-2H-fcc Au-CuJNS (84.3%, 55.5%) > fcc-2H-fcc Au-Cu CAH (75.7%, 50.5%) > fcc-2H-fcc Au-Cu CSN (70.3%, 50.2%) > commercial fcc Cu NP (65.7%, 43.6%) > Au+Cu mixture (37.3%, 21.5%). Compared with fcc-2H-fcc Au-Cu CAH, fcc-2H-fcc Au-Cu CSN and commercial fcc Cu NP, fcc-2H-fcc Au-CuJNS also shows a strong affinity for C at -1.1 V (relative to RHE). 2+ The product has a 6.08 mA cm -2 The maximum partial current density ( Figure 44 ).

[0236] Also compared to C 2+ / C1 product ratio, which can largely reflect the CC coupling efficiency in CO2RR ( Figure 45 ). Notably, fcc-2H-fcc Au-Cu JNS exhibits the highest C of 11.4 2+ / C1 product ratio, which is much larger than that of fcc-2H-fccAu-Cu CAH (6.4), fcc-2H-fcc Au-Cu CSN (5.0), commercial fcc Cu NP (3.6) and Au+Cu mixture (3.1), indicating the efficient CC coupling process on fcc-2H-fcc Au-Cu JNS. In addition, the CO2RR performance of fcc-2H-fcc Au-CuJNS is improved in four aspects (including FE of C2H4, CEE of C2H4, C 2+ FE and C of the product 2+ / C1 ratio) is much better than that of the reported catalysts with similar heterogeneous structures ( Figure 46 ).

[0237] The catalytic stability of fcc-2H-fcc Au-Cu JNS was evaluated via long-term CO2 electrolysis in an H-type cell at -1.1 V (vs. RHE). After 10 h of operation, the current density showed no significant decrease, and the FE of C2H4 could still reach 50% ( Figure 47 Importantly, after durability testing, fcc-2H-fcc Au-Cu JNSs can still largely maintain their composition and unique morphology ( Figure 48A and 48B ), and unconventional fcc-2H-fcc heterophases in Au and Cu domains ( Figure 49 The aforementioned results demonstrate the excellent catalytic properties and structural stability of fcc-2H-fcc Au-Cu JNSs for CO2 electroreduction.

[0238] To evaluate the potential of fcc-2H-fcc Au-Cu JNSs as catalysts for practical applications, their CO2RR performance was further tested in a flow cell using 1 M potassium hydroxide (KOH) aqueous solution as the electrolyte ( Figures 50A to 50C Impressively, the fcc-2H-fcc Au-Cu JNS exhibits the highest FE of 50.1% for C2H4 with a partial current density of 180.5 mA cm at −1.7 V (vs. RHE). -2 Meanwhile, fcc-2H-fcc Au-Cu JNS has a great influence on the 2+ The product achieved a highest FE of 61.3% and a partial current density of 220.8 mA cm at −1.7 V (vs. RHE). -2 , exceeding the industrially relevant current density threshold (200 mA cm -2 These results reveal that fcc-2H-fcc Au-Cu JNS can be used as high-performance catalysts for electrochemical CO2RR to obtain high-value C under practical conditions. 2+ Huge potential of the product.

[0239] Example 8

[0240] In situ mechanism studies

[0241] In order to further study the C 2+ The key adsorbed intermediates during electrochemical CO2RR were monitored and identified using in situ ATR-FTIR spectroscopy to promote the formation of products. Figure 51 As shown, starting from -0.3 V (vs. RHE), several peaks were found in the ATR-FTIR spectrum, which can be assigned to the corresponding CO2 reduction intermediates. Specifically, around 2046 and 1944 cm -1 The peaks at are attributed to the top-site and bridge-site configurations of CO* adsorption on the Cu surface, respectively.

[0242] like Figures 52A to 52C As shown in Figure 3, compared with the only top-site adsorption of CO* on commercial fcc Cu NPs and Au+Cu mixtures, the appearance of bridge-site adsorption of CO* was also observed on fcc-2H-fcc Au-Cu JNS. This unique bridge-site adsorption of CO* on fcc-2H-fcc Au-Cu JNS may originate from the presence of an unconventional phase Au-Cu interface, which is not present in commercial fcc Cu NPs or Au+Cu mixtures. It is believed that the coexistence of top-site and bridge-site adsorption configurations of CO* is beneficial for CC coupling and thus for C 2+ In addition, the OCCOH* peaks (about 1531 and 1180 cm -1 ) and OC2H5* peaks (about 1343 and 1148 cm -1 ) is more obvious than the peaks on commercial fcc Cu NPs and Au+Cu mixtures, especially at about 1531 cm -1 It is worth noting that OCCOH* and OC2H5* are key intermediates in the generation of C2H4 and C2H5OH in CO2RR, respectively. This result further confirms that CC coupling is enhanced on fcc-2H-fcc Au-Cu JNS compared with commercial fcc Cu NPs and Au+Cu mixtures. These observations indicate that the CO* adsorption configuration is diverse on fcc-2H-fcc Au-Cu JNS and that the reaction pathway is oriented towards C via enhanced CC coupling. 2+ produce.

[0243] In situ DEMS was also applied to understand the CO2 reduction process on fcc-2H-fcc Au-Cu JNS. Under CO2RR conditions, the CO2 reduction reaction was performed at 5 mV s-1 The in situ DEMS spectra of the catalyst were collected by linearly scanning the potential from 0 to -1.3 V (equivalent to RHE) at a scan rate of 100 nm. Several peaks were detected in the DEMS spectrum, which corresponded to H2, CO, CH4 and C2H4 ( Figures 53A to 53D ).like Figure 53A As shown in Figure 3, the CO onset potential on fcc-2H-fcc Au-Cu JNS is between that on Au+Cu mixture and commercial fcc Cu NPs. This result indicates that the combination of Au and Cu components does help to reduce the overpotential for CO formation, which is a key source / intermediate for CC coupling. And the delayed observation of CO on fcc-2H-fcc Au-Cu JNS compared to Au+Cu mixture may be due to the overflow of CO from Au domains to Cu domains. In addition, for the generation of C2H4, fcc-2H-fccAu-Cu JNS exhibits the least negative onset potential, followed by Au+Cu mixture and then commercial fcc Cu NPs ( Figure 53B These findings further reveal that the formation of unconventional Au-Cu interface has an important effect on the C 2+ Generation is very important.

[0244] Example 9

[0245] Theoretical calculations

[0246] To reveal the influence of unconventional phase JNS on CO2RR performance, density functional theory (DFT) calculations were further applied to investigate the differences in electronic structure and reaction trends between 2H / fcc Au-Cu and fcc Au-Cu JNS. F ), the bonding orbital distribution on the 2H / fcc Au-Cu JNS surface is stronger than that on the fcc Au-Cu JNS surface ( Figure 54A and 54B This is induced by the introduction of the unconventional 2H phase, which ensures efficient electron transfer to the intermediate. The structure of the 2H / fcc Au-Cu JNS remains stable after relaxation, with only minor lattice distortions observed. This confirms the stability of the combined Janus and heterogeneous structures in the 2H / fcc Au-Cu JNS.

[0247] We then further compared the projected partial density of states (PDOS) of 2H / fcc and fcc Au-Cu JNS ( Figure 55A and 55B It is worth noting that the unique 2H phase does not significantly change the overall electronic structure, where the Cu-3d orbitals in the E FThere are obvious sharp peaks near E for 2H / fcc and fcc Au-Cu JNS, respectively. V -1.65eV(E V represents 0eV) and E V -1.67eV. The Au-5d orbital is located deeper and covers a wide range from E V -1.0eV to E V -7.0 eV. Such electron-rich features suggest that the Au domain acts as an electron reservoir to support electron transfer to the intermediate through the Cu site. Although the overall PDOS shows limited changes, further investigation of the site-dependent PDOS demonstrates the influence of Janus structure and heterogeneity. For the Cu site, a gradual upward shift of the 3d orbital from the fcc bulk to the 2H surface ( Figure 56A ). Compared with the fcc phase, the overall Cu-3d orbital shifts upward, which proves that the 2H phase is crucial for improving the electroactivity of the Cu site in the CO2RR process. In contrast, the electronic structure evolution of the Au-5d orbital is also obvious ( Figure 56B ). For the fcc phase, the Au-5d orbitals have moved from the bulk to the surface, which is attributed to the change in the coordination environment.

[0248] For the surface sites on the 2H phase, the interface with the Au-fcc phase exhibited the lowest electroactivity, while the pristine 2H surface sites showed a distinct peak with improved electroactivity. Site-dependent PDOS has confirmed that the 2H phase is the key active site for promoting the CO2RR performance. The d-band centers of the Cu-3d and Au-5d orbitals ( Figure 57 ). For the Cu site, 2H / fcc Au-Cu JNS exhibits a higher d-band center than fcc Au-Cu JNS, which is attributed to the formation of the highly electroactive 2H phase. More importantly, note that the pristine 2H / fcc Cu shows an even higher d-band center, further confirming that the superior electroactivity is primarily determined by the 2H phase of Cu. At the same time, the Au-5d orbital delivers a different trend in d-band centering, with 2H / fcc Au-Cu JNS showing a higher d-band center than both fcc Au-Cu and 2H / fcc Au. This demonstrates that the improved electroactivity of the Au-5d orbital originates from the interaction between 2HCu and 2H Au, which also benefits the overall electroactivity in 2H / fcc Au-Cu JNS.

[0249] In addition to the electronic structure of the metal site, the PDOS of the key adsorbate formed by C2H4 is revealed ( Figure 58For the 2H surface, the s,p orbitals of the intermediates show a good linear relationship from the initial CO2-to-CC coupling and subsequent hydrogenation, where the downshift of the s,p orbitals provides for an efficient reduction process. In contrast, the s,p orbitals show a very weak linear relationship on the fcc surface, which may induce a higher energy barrier for the reduction process.

[0250] The CO2 reduction process was also theoretically studied from an energy perspective. The adsorption of the initial reactant CO2 was strongest on the 2H / fccAu-Cu JNS, especially near the 2H interface between Au and Cu ( Figure 59 ). It is noteworthy that fcc Au-Cu JNS showed a much weaker preference for CO2 adsorption even compared with 2H / fcc Au and 2H / fcc Cu. These results indicate that the introduction of the 2H phase is important for improving the adsorption preference of CO2. As a key intermediate in CC coupling, the adsorption of CO* is another important criterion ( Figure 60 ). Note that the fcc phase and the 2H phase show different CO spillover trends. CO* prefers to migrate from fcc Au to fcc Cu, and there is an energy barrier at the fcc Au / Cu interface. However, CO* on both 2H Cu and 2H Au tends to migrate to the 2H Au / Cu interface, supporting the idea that the unconventional Au / Cu interface is the catalyst for CC coupling and C 2+ The large energy difference on the 2H phase also ensures more efficient CO* spillover. Due to the higher energy preference for Cu, Au and interface sites, CO* spillover from the fcc to the 2H phase is also possible. The flexible CO* spillover mode ensures efficient CC coupling on the 2H / fcc Au-Cu JNS ( Figure 61 ). Therefore, the C-C coupling on 2H / fcc Au-Cu JNS shows a significantly stronger trend than that on fcc Au-Cu JNS due to the improved CO* adsorption, which leads to the 2+ The product has a higher FE.

[0251] In order to reveal the overall reaction trend, the reaction trends of C2H4 generation on 2H Au-Cu and fcc Au-Cu were compared ( Figure 62 ). 2H Au-Cu greatly reduces the energy barrier for CO2RR, where the rate-determining step (RDS) is the hydrogenation of OCCO* with a barrier of 0.77 eV. fcc Au-Cu has the same RDS but a greatly increased barrier of 1.76 eV, which significantly reduces the efficiency of C2H4 generation. In addition, the formation of CO* on fcc Au-Cu JNS also has a 1.0 eV barrier from CO2 to COOH*, which hinders CC coupling, leading to C 2+The overall reaction energy of 2H Au-Cu is lower than that of fcc Au-Cu, which supports the selectivity of C 2+ These results well explain the role of fcc-2H-fcc Au-CuJNS in promoting the efficient conversion of CO2 to high-value C 2+ The structural advantages of the product.

[0252] The present invention has been presented by way of example only, and various other modifications and / or alterations may be made to the described embodiments by those skilled in the art without departing from the scope of the invention as specified in the appended claims.

Claims

1. A nanomaterial, comprising: Au nanostructures; as well as providing a Cu nanostructure having the Au nanostructure; The Au nanostructure and the Cu nanostructure are each in a different phase. 2 . The nanomaterial of claim 1 , wherein the Cu nanostructure is provided on and above the Au nanostructure. 3 . The nanomaterial according to claim 1 , wherein the Au nanostructure and the Cu nanostructure are both in the form of fcc-2H-fcc heterophase structures. The nanomaterial of claim 1 , wherein the Cu nanostructure covers a first portion of the Au nanostructure. The nanomaterial according to claim 4 , wherein the second portion of the Au nanostructure is covered by a surfactant. The nanomaterial of claim 1 , wherein the Au nanostructures are in the form of fcc-2H-fcc Au nanorods. 7 . The nanomaterial of claim 6 , wherein the fcc-2H-fcc Au nanorods have a first portion covered by a fcc-2H-fccCu nanostructure.

8. The nanomaterial of claim 7, wherein the fcc-2H-fcc Au nanorods and the fcc-2H-fccCu nanostructures are arranged in a substantially lattice-matched manner.

9. The nanomaterial of claim 7, wherein the fcc-2H-fcc Au nanorods include a second portion at least partially covered by a surfactant.

10. The nanomaterial according to claim 9, wherein the surfactant comprises any one of oleylamine and dodecylamine.

11. The nanomaterial according to claim 1, wherein the fcc-2H-fcc Au nanostructure and the fcc-2H-fcc Cu nanostructure are arranged in the form of a Janus nanostructure.

12. The nanomaterial of claim 7, wherein the first portion of the fcc-2H-fcc Au nanorods is circumferentially covered by the fcc-2H-fcc Cu nanostructure. 13 . The nanomaterial according to claim 10 , wherein the first portion is arranged between two second portions on the fcc-2H-fcc Au nanorod, and at least one of the two second portions is at least partially covered by the surfactant. 14 . The nanomaterial of claim 13 , wherein at least one of the two second portions is at least partially covered by fcc Cu atoms of the fcc-2H-fcc Cu nanostructure.

15. The nanomaterial according to claim 14, wherein the fcc-2H-fcc Au nanorods and the fcc-2H-fccCu nanostructures are arranged in the form of a coaxial heterogeneous nanostructure. The nanomaterial according to claim 6 , wherein the fcc-2H-fcc Au nanorods are wrapped by the fcc-2H-fccCu nanostructures.

17. The nanomaterial according to claim 16, wherein the fcc-2H-fcc Au nanorods and the fcc-2H-fccCu nanostructures are arranged in the form of fcc-2H-fcc Au-Cu core-shell nanostructures.

18. A method for preparing the nanomaterial according to claim 1, comprising the following steps: a) providing a reaction mixture comprising fcc-2H-fcc Au nanostructures, a reducing agent, and a copper precursor; b) heating the reaction mixture for a predetermined period of time, and then cooling the reaction mixture to room temperature; and c) separating the nanomaterial from the reaction mixture.

19. The method of claim 18, wherein the reaction mixture further comprises a surfactant.

20. The method of claim 19, wherein the reaction mixture is provided by adding the copper precursor at a predetermined rate to a solution mixture comprising the fcc-2H-fcc Au nanostructures, the surfactant, and the reducing agent at an elevated temperature.

21. The method of claim 18, wherein the reducing agent comprises any one of 1,2-hexanediol, 1,2-hexadecanediol, and 1,2-butanediol.

22. The method of claim 19, wherein the surfactant comprises a mixture of oleylamine and dodecylamine.

23. The method of claim 22, wherein oleylamine and dodecylamine have a volume ratio of 2:

3.

24. The method of claim 18, wherein the copper precursor comprises copper acetylacetonate.

25. The method of claim 20, wherein when the reducing agent comprises 1,2-hexanediol, the copper precursor is heated at 0.094 mL min -1 was added to the solution mixture at a rate of .

26. The method of claim 20, wherein when the reducing agent comprises 1,2-hexadecanediol, the copper precursor is heated at 0.062 mL min -1 was added to the solution mixture at a rate of .

27. The method of claim 20, wherein when the reducing agent comprises 1,2-butanediol, the copper precursor is heated at 0.5 mL min -1 was added to the solution mixture at a rate of .

28. The method of claim 20, wherein the elevated temperature is 110°C to 130°C.

29. The method of claim 18, wherein the fcc-2H-fcc Au nanostructures are provided in the form of fcc-2H-fcc Au nanorods.

30. The method of claim 18, which is a seed growing method.

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